kc3-lang/gnulib/doc/posix-functions/readlinkat.texi

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• Hash : a2549454
  Author :
  Date : 2020-12-13T16:48:26
  

  readlink, readlinkat: add ERANGE portability
  
  Fix some portability issues with Gnulib's readlink and readlinkat,
  notably mostly working around the ERANGE problem in AIX and HP-UX.
  * doc/posix-functions/readlink.texi:
  * doc/posix-functions/readlinkat.texi:
  ERANGE problem is mostly fixed now.  Mention AIX problem with
  trailing / and EINVAL.  Lessen differences between these two files.
  * lib/readlink.c (rpl_readlink):
  * lib/readlinkat.c (rpl_readlinkat):
  If stat ("FILE/", ...) reports EOVERFLOW, treat FILE/ as an
  existing directory.  Mostly work around READLINK_TRUNCATE BUG.
  Lessen spurious differences between the readlink and readlinkat code.
  * lib/readlinkat.c (rpl_readlinkat):
  Fix bug where stat was used where fstatat was intended.
  * m4/readlink.m4 (gl_FUNC_READLINK):
  Rename gl_cv_func_readlink_works to gl_cv_func_readlink_trailing_slash
  to identify readlink problems more precisely.  All uses changed.
  Guess no on AIX or HP-UX for this variable.
  Add check for whether readlink truncates results,
  and define new macro READLINK_TRUCATE_BUG accordingly.
  * m4/readlinkat.m4 (gl_FUNC_READLINKAT):
  Also check gl_cv_func_readlink_trailing_slash when deciding
  whether to replace readlinkat.
  * modules/readlinkat (Depends-on): Most dependencies are also
  needed if replacing readlinkat.  fstatat is different, as it
  is needed only if replacing an existing readlinkat.
  

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• doc/posix-functions/readlinkat.texi

• @node readlinkat
  @section @code{readlinkat}
  @findex readlinkat
  
  POSIX specification:@* @url{https://pubs.opengroup.org/onlinepubs/9699919799/functions/readlinkat.html}
  
  Gnulib module: readlinkat
  
  Portability problems fixed by Gnulib:
  @itemize
  @item
  This function is missing on some platforms:
  glibc 2.3.6, Mac OS X 10.9, FreeBSD 6.0, NetBSD 5.0, OpenBSD 3.8, Minix 3.1.8, AIX 5.1, HP-UX 11, IRIX 6.5, Solaris 10, Cygwin 1.5.x, mingw, MSVC 14, Android 4.4.
  But the replacement function is not safe to be used in libraries and is not multithread-safe.
  @item
  Some platforms mistakenly succeed on file names ending in @file{/}:
  OS X 10.10.
  @item
  On some platforms, this function returns @code{int} instead of
  @code{ssize_t}:
  AIX 7.1.
  @end itemize
  
  Portability problems mostly fixed by Gnulib:
  @itemize
  @item
  On some platforms, this function fails and sets @code{errno} to
  @code{ERANGE} rather than returning truncated contents:
  AIX 7.2.
  The Gnulib replacement normally works as POSIX requires by returning
  the truncated contents.  However, if the full link contents are
  unreasonably large (more than 4000 bytes) the replacement clears the
  entire buffer and returns the buffer size; although this is not a
  complete fix, it suffices for typical callers, which ignore the buffer
  contents anyway.
  @end itemize
  
  Portability problems not fixed by Gnulib:
  @itemize
  @item
  This function always fails on platforms that don't support symlinks:
  mingw, MSVC 14.
  @item
  When this function is called on a directory: In the case of NFS mounted
  directories, Cygwin sets @code{errno} to @code{ENOENT} or @code{EIO} instead of
  @code{EINVAL}.  To avoid this problem, check for a directory before calling
  this function.
  @item
  When this function is called on a file that is not a symbolic link:
  IRIX may set @code{errno} to @code{ENXIO} instead of @code{EINVAL}.  Cygwin
  may set errno to @code{EACCES} instead of @code{EINVAL}.
  @item
  When this function fails because it is called on an existing
  non-directory's name concatenated to @file{/},
  it sets @code{errno} to @code{EINVAL}:
  AIX 7.2.
  @item
  Symlink contents do not always have a trailing null byte, and there is
  no indication if symlink contents were truncated if the return value
  matches the length.  Furthermore,
  Linux sets @code{errno} to @code{EINVAL} if the
  requested length is zero.  Use the gnulib module @code{areadlink} for
  improved ability to read symlink contents.
  @end itemize
  

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